Work on getting ur MR rank up, u are close to 7 and the Soma Prime is very powerful, also the Kohm is great for destroying mobs. Start doing Defense missions and collect relics and then open them for prime parts (also start getting Forma BP's from relic runs so u can start getting some powerful weapons). Start leveling up any weapons and frames u have.

Get Rhino as he is unkillable for most of the game his 3 will buff any weapon for a lot of damage. Start learning ur favorite warframes abilities and use them constantly to help make up for ur weapons. Start leveling basic mods for survival and damage. Start working on Steel Meridian syndicate rank. Start working on ur Cetus and Fortuna standing (build powerful Zaws and Kitguns). Start soloing missions ur comfortable with and grab as many resources as u can (find those stars), do the weekly Ayatan statue missions to get free Endo (1.5K-3K a pop).